1. Field of the Invention
This invention generally relates to communication devices having access to password-protected voicemail services. It is especially useful for mobile wireless communication devices having stored password data for automated use with automated voicemail access capability.
2. Related Art
Voicemail facilities are now a well known feature of virtually all telephone systems. Most voicemail services are password protected such that access even by an authorized user is only permitted if a predefined secret password is appropriately entered.
Mobile or wireless communication devices may also be used to access such voicemail facilities. Often, such portable wireless communication devices include the ability to pre-store the telephone number utilized for access to the voicemail features—quite often including the requisite password data (e.g., as an appendage to the access telephone number or as a second pseudo-telephone number to be dialed in succession after a connection has been established to the voicemail facility via the first telephone number). Of course, voicemail facilities can also be manually accessed by user manipulation of the usual keyboard—including entry of the requisite password for access to voicemail data.
It is typical and conventional for audible feedback to be provided to the user of such communication devices. Typically, a distinctly discernible tone is generated and made audible to the user for each digit of the access telephone number and password. Quite often, the audible feedback may be the usual DTMF tones that were traditionally used for transmitting key stroke data from a user to a telephone switch facility in a traditional POTS. If alternate feedback audible tones are utilized, they have also conventionally been uniquely associated with particular digit values. That is, there has traditionally been a one-to-one unique correspondence between a given tone frequency (or combination of frequencies in the case of DTMF tones) and a particular digit value being keyed manually or automatically transmitted.
If a portable (i.e., wireless) communication device includes an automated voicemail access feature (including the required password), then an unauthorized user (e.g., a pickpocket or attacker) may obtain possession of the device and make unauthorized phone calls—including unauthorized access to voicemail services. In doing so, if there is some humanly detectable feedback that identifies the values of the password data being transmitted, then the unauthorized user may learn the value of the secret password during a period of unauthorized possession. If so, such information may even be obtained without the legitimate user knowing that such unauthorized access has taken place and thus present a security risk for future password protected voicemail services. For example, the unauthorized user might use an audio recorder to simply record the sequence of tones and then, knowing the unique correspondence between tone frequency and digit values, play back the recorded tones to ascertain the voicemail password value.
For at least such reasons, enhanced security for voicemail passwords is desirable.